With the continuous development of a mobile terminal, the volume of the mobile terminal is also getting smaller and smaller, and it will also become a trend that originally the original common functions of the mobile terminal are transferred to the base, for example, the majority of smart phones cancel a full keyboard function, and the full keyboard input function can be provided on the base; alternatively, since the supply of the space of the audio equipment in the mobile terminal is small to cause the limited sound efficiency, better audio equipment is provided through the base. In order not to affect the standby time of the mobile terminal, the power sources of the new equipment should be provided by a dedicated battery, that is a base battery, furthermore there is a charging circuit for the base battery.
In the existing technology, there are generally two cases for the base to charge the mobile terminal and the own base battery. The first one is that the base with a base charger is connected with the mobile terminal, and when the mobile terminal is charged, the state of being charged will be maintained until the base is separated from the mobile terminal artificially, and then the base charger will charge the base battery. The second one is that the base with the base charger charges the base battery as well as the mobile terminal battery at the same time, thus resulting in a very low efficiency and too long charging time. In addition, the base will keep a charging state when charging the mobile terminal via the own base battery, so that the base battery is prone to the over-discharge phenomenon.